Making the Setting Unique - The Red Comet

Okay, I whined once about the lack of orginality in this campaign world. I have at least one little twist which has almost certainly been done before, but I haven't experienced it (I'll check after I post so as to not be too depressed by how much this idea has been done before...)

Anyway, the thing is that there's a comet caught in the sun's (or probably the planet's) orbit - so it appears as a bit of a "second sun" (at night) or whatever in the sky (I'm wanting it to be pretty big and red...). Anyway, it's on an unsteady orbit around the sun, and eventually it will collide with the planet. It's already causing all kind of chaotic effects to magic and even to the natural order of things. I'm thinking that the comet will be the reason that the barrier between Daen-Ral and the Old Lands is beginning to crumble. The comet is also the harbinger of the awakening of the Old Gods - the elemental gods of chaos and (generally) evil.

So there would be cults dedicated to the worship of the Comet - there would be seers/astrologers who realize that the comet is going to eventually crash into the planet (in relatively short order, I'm thinking - short meaning something like 10-25 years). There would be those who would try to stop it, those who would want to encourage it (especially the worshippers of the gods of chaos). Most would ignore it. How long has it been in the sky? A generation? A hundred generations? Longer is better, since those who claim the sky is falling would be seen as crazies, even though it really is. I have some images of the beginning of Independence Day (when people are trying to welcome the aliens) or all the craziness in the movie Contact.

Questions:

How long has it been there?

How long til it crashes?

Can it be stopped?

What caused it to now begin to turn toward the planet?

What will be the effects of the comet crashing into the planet?

How is it affecting magic?

How is it affecting the tides, techtonics, atmosphere?

What groups/cults/whatever have sprung up and why? What are their goals? How do they cooperate with or oppose one another? What does the church have to say? The Old Gods? The Druids?

EDIT: the comet will fill the NIGHT sky - brighter than the full moon, but not nearly as bright as day - or maybe as bright as the full moon - and that way there would be double shadows as they would be on the opposite parts of the sky...hmmm..... It could mess with thieves' abilities to a degree...

Would darkness seen doubly dark if there are two sources of light?

What if the comet is "killing off" the Elves and has driven the Dwarves deeper underground?

Or...well, how WILL it affect the races & creatures?

How will monsters be affected?

NOTE image was found online...no idea who the copyright holder is....